Question: Who was the Chairperson of University of waterloo while that post was came to an end in 1981
Paraphrase: When the University of Waterloo's post came to an end, who was the chairperson?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q1049470 p:P488 ?s . ?s ps:P488 ?obj . ?s pq:P582 ?x filter(contains(YEAR(?x),'1981')) }